Catch rate trends for brown trout and mountain whitefish paralleled those for rainbow trout in the 

 Snoball section; although they were consistently lower (Figure 10). Proportion of catch by 

 species was consistent in Snoball during pre-whirling disease years in contrast with post-whirling 

 disease data for the Pine Butte section. However, this data should be viewed with the caveat that 

 catch rates can be affected by factors such as weather, flows, and other climatic conditions that 

 may not be reported as part of the creel survey. The Snoball section is not as valuable for 

 examining the impact of whirling disease because of a lack of post- whirling disease catch rate 

 data, but is included as a reference for comparison with earlier Pine Butte data. 



a 



a 



a 



OS 



u 



1.2 

 1 

 0.8 

 0.6 

 0.4 

 0.2 

 



E3 Rainbow 



Brown 

 D Mountain Whitefish 



1975 



1976 



1977 



1981 



Year 



Figure 10. Catch rates in fish per hour for the Snoball section of the Madison River, Montana fi-om 1977 

 to 1981. The Snoball section was closed to boat fishing in 1975 and closed to all fishing in 1977. 



Catch rates for rainbow trout in the Pine Butte section were much lower in 1995 (0. 19 fish per 

 hour) than in 1981 (0.63 fish per hour) (Figure 1 1). The catch rates for brown trout did not show 

 a similar pattern, and actually increased from 0. 12 fish per hour in 1977 to 0.33 fish per hour in 

 1995 (Figure 1 1). It appears that as whirling disease was reducing the numbers of rainbow trout, 

 the brown trout population became proportionately more available for capture by anglers. The 

 data for mountain whitefish is less complete, but does show a slight increase fi-om 0. 19 fish per 

 hour in 1977 to 0.24 fish per hour in 1995, the only two years with data available (Figure 1 1). 

 Again this increase may reflect a shift in the proportion of each species available in the Madison, 



Evaluation of 199S and 1996 Creel Data and its Implications related to Whirling Disease 

 In the Madison River, Montana 



Montana Fish, Wildlife and Paries 

 March 12, 2002 



23 



